2 Journal New York Entomological Society. [Voi. viii. 



It is with pleasure that I acknowledge the aid of Professor Corn- 

 stock and his able corps of assistants ; without this and the resources 

 of the entomological department of Cornell University, which were 

 put at my disposal, this investigation would have been impossible. 



The LiFE-His'i'ORV of F/rn's. 



The observations on the number and duration of the stages of this 

 insect were made on the July brood, which is one of the four broods 

 of the year. The butterfly lays its eggs upon the food-plant of the 

 caterpillar, sticking one at a time upon the leaves at varying dis- 

 tances. The egg hatches in from four to five days. As the cater- 

 pillar emerges, the head measures .36 mm. Excepting the first, the 

 ratio of increase in head measurement at each moult is 1.55 ; in the 

 case of the first moult it is slightly greater. 



The caterpillar moults for the first time in from 30 to 48 hours 

 after hatching. The head measures after this moult .6 mm. I'he cat- 

 erpillar moults for the second time in from two to three days after the 

 preceding moult, and the head measures .93 mm. In one day it 

 moults again, and the head measures 1.44 mm. In one day more it 

 moults again, and the head measures 2.22 mm. After four days it 

 moults for the pupa, and seven days later the adult emerges. The 

 butterflies pair when about 24 hours old, and the female at once be- 

 gins to lay the eggs for a new brood. The whole life-cycle covers a 

 period of about 22 days. The time of these changes varies some- 

 what with the nourishment and the temperature. These points are 

 summed up in the following table : 



j;gg 4 to 5 days. HEM. MEASUREMENT. 



1st larval Stage 30 to 48 ho"'* 36 mm. 



2d " " 2 to 3 days -6 mm. 



,d <. << . . iday .93mm. 



4th " " i^i^^y • • • •^•44--- 



^ ,^,., f 3 days active. ) .2.22 mm. 



5th " 4aa>s 1^ I (Jay hung up. 1 ' 



Pupa - . • 7 days. 



Emergence to egg layhig (Pair in 24 hours, begin to lay almost immediately). 



The caterpillar eats much and grows rapidly, and seemingly has 

 nothing to do but to store up energy and fat to bring out the adult 

 insect. 



